Approximately 20% of workers in industrialized nations work nonstandard schedules such as rotating and night shifts. Shift workers frequently report sleep disturbances, fatigue while working, and impaired performance. As a result, many workers take medications in order to counterbalance abrupt shift change-related negative effects. Recently, we developed a naturalistic laboratory model of shift work and have begun characterizing drug effects on individuals working irregular schedules. In the proposed studies, we will expand our evaluations of drug interactions with workplace contingencies by evaluating the effects of modafinil and marijuana on workplace-relevant behaviors during day shift and night shift work. The results from these studies may be of particular significance in occupations that require abrupt changes in work schedules, e.g., health care workers, police officers, and military personnel. Further, using our carefully-controlled, residential laboratory procedures, we will begin a systematic evaluation of the effects of more recent relevant abused "club drugs" MDMA and GHB on workplace performance. Our studies on club drugs will also evaluate the effects of methamphetamine alone, and the effects of drug combinations. In these studies, the effects of acute and repeated club drug administration on performance the day of administration, as well as on performance the morning after administration, i.e., "hangover," on a variety of behaviors relevant to workplace performance will be determined. Despite the fact that club drugs are frequently used by the working public, there is a limited database evaluating their effects on workplace-relevant behaviors. The results from these studies will provide for the first time a scientific database about the workplace-related consequences of acute and repeated dosing of several popular club drugs. Together, the data from the proposed studies will have substantial public health impact and will serve both educational and public policy functions.